[Lldb-commits] [PATCH] D55434: ObjectFileBreakpad: Implement sections

Greg Clayton via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Mon Dec 10 10:25:54 PST 2018

clayborg added a comment.

In D55434#1325739 <https://reviews.llvm.org/D55434#1325739>, @labath wrote:

> In D55434#1323912 <https://reviews.llvm.org/D55434#1323912>, @clayborg wrote:
> > If you plan on not making the breakpad file ever stand alone, then you will need to take any addresses and look them up in the module section list and use the other sections. I don't see why the breakpad file can't be stand alone though. It won't be as accurate, but it sure would be nice to be able to load a bunch of them into LLDB without needing to find the original executable and just symbolicate no?
> I could try to make it stand-alone, but that seems to me like a duplication of effort. And since the sections I could conjure up from the breakpad info would never match the original elf file, I would have to support both cases anyway, one with using the sections from the object file, and one with the own, made-up sections.
> I do intend to support both cases, but in a slightly different way. The way, I see it we have actually four cases to consider:
> 1. we have an stripped elf file, and a breakpad symbol file (the case of an unstripped elf file is uninteresting, as it will have much better debug info than breakpad can possibly provide)
> 2. we don't have an elf file, but we have a breakpad file
> 3. we don't have an elf file nor a breakpad file
>   Because of case 3, we have to do some section conjuring independently of any breakpad file. We already do that to some extent, and @lemo is getting ready to extend that in D55142 <https://reviews.llvm.org/D55142>. Once we have that, and we find a breakpad file for this module (case 2), the breakpad file should be able to just latch onto the sections created for the placeholder object file. And I believe ProcessMinidump is in a better position to create the "placeholder" sections, as it has both access to the load addresses and sizes of the modules. From breakpad info, it would be hard to determine the size of the module if the highest address is occupied by a "PUBLIC" symbol, as they don't have any sizes associated with them.
>   Going back to case 1, if we have a stripped elf file, the breakpad file should latch onto the sections of that one without ever knowing the difference. So in the end, I hope this will produce a clearer code because the concerns will be separated. Breakpad code will always deal with externally-provided sections, regardless of whether they come from a "real" object file, or a made-up one. And the "making-up" code can work independently of there being a breakpad file.

Ok. Check out my changes that parse region info:

It parses the memory region info from the linux maps info if it is available. In breakpad generated minidumps, this will give us enough info to correctly create sections for all  object files in case #3!



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